This invention pertains to ballistics and, more particularly, to a lubricating grease, ammunition, and process for extending the life of a barrel of a weapon.
Throughout history, mankind has developed weapons for hunting and military purposes. Modern weapons fire projectiles, such as bullets, artillery shells, missiles, etc. Various weapons for shooting projectiles include firearms, such as guns and rifles, bazookas, automatic weapons, such as machine guns, semiautomatic rifles, and large caliber weapons such as cannons, howitzers, and rockets. The desirability of a weapon depends upon its size, accuracy, mobility, safety, shooting distance, and impact and penetration characteristics of the projectiles fired from the weapon.
Firing of projectiles from a weapon causes some degree of erosion (physical wear) and corrosion (chemical wear) of the barrel of the weapon through which the projectile is shot. The severity of the erosion and corrosion can undesirably widen the bore of the weapon, deform the barrel, and adversely affect the accuracy of the projectile and the safety of surrounding personnel.
Erosion of the barrel is caused by metal to metal contact between the ammunition and the barrel as the projectile is shot out of the weapon. Many weapons use spiraling (rifling) to spin the projectile in order to stabilize its flight. In such weapons, either the projectile, normally the case with small firearms, or the projectile's rotating band, normally the case with larger weapons, are of slightly larger diameter than the land diameter of the barrel. As the projectile is fired, the lands or spiraled rifling ridges in the bore engraves the projectile or its rotating band to impart a rotation as the projectile passes through the barrel. Such rotation enhances the stability, range, and accuracy of the projectile, but causes bore erosion. Bore erosion is particularly severe in high muzzle velocity weapons.
Corrosion of the barrel is typically caused by nitrates, phosphates, or other corrosive gases emitted from the propellant of the ammunition upon firing the projectile. These corrosive gases, by reason of their high temperature and velocity, tend to soften, melt, and remove microscopic portions of the gun barrel material from the bore surface of the weapon each time a round is fired. Because of the direct contact between the flow of hot propellant gases and the bore surface, a considerable amount of heat is transferred to the gun barrel with each round fired. Under conditions of sustained rapid fire, the temperature of the barrel of the weapon can increase to a level which may exceed the deformation or melting point of the metal in the weapon and causes the barrel to deform or deflect. With a sustained rate of fire which produces a net heat input to the barrel greater than that which can be dissipated, the ammunition chamber can become so hot that it may accidentally and prematurely detonate and misfire rounds of ammunition placed therein which can injure nearby personnel and damage the weapon.
In various weapons and particularly automatic weapons, rapid, repetitive, or high muzzle-velocity firing creates a lot of rapidly expanding hot propellant gases which can overheat the barrel and increase the rate of bore corrosion. Overheated barrels increase the amount and severity of wear. This problem is so acute with machine guns that they are usually built with quickchange barrels. A machine gun can easily wear out a dozen or more barrels before the remaining parts of the weapon are worn out. It is not uncommon for barrels to be fired until the heat destroys them. It is apparent that significantly reduced heating and bore wear could significantly improve weapon effectiveness in such circumstances and extend the service life of the weapon.
In large caliber weapons, bore corrosion is less a consequence of direct mechanical interaction of the ammunition with the barrel than of gas corrosion. Hot propellant gases often expand through minor cracks in the barrel surface of large caliber weapons around the projectile. Gas pressures and temperatures can exceed 40,000 psi and 2,000.degree. F. downstream of the projectile, which can be detrimental to the longevity and structural integrity of the barrel.
Over the years, a variety of greases, ammunition, and processes have been developed to decrease bore erosion and corrosion. Typifying such greases, ammunition, and processes, as well as other types of greases, are those found in U.S. Pat. Nos. 34,031, 126,614, 407,890, 440,672, 499,487, 587,342, 627,929, 802,301, 819,518, 1,039,774, 1,189,011, 1,191,178, 1,376,316, 1,481,930, 1,678,162, 2,011,249, 2,193,631, 2,360,473, 2,398,695, 3,095,376, 3,097,169, 3,130,671, 3,208,387, 3,313,727, 3,322,020, 3,267,035, 3,356,029, 3,429,261, 3,488,721, 3,565,802, 3,580,178, 3,828,678, 3,907,691, 3,942,408, 3,997,454, 4,089,790, 4,100,080, 4,100,081, 4,108,044, 4,155,858, 4,163,729, 4,196,670, 4,203,364, 4,239,006, 4,334,477, 4,353,282, 4,395,934, 4,417,521, 4,454,175, 4,465,883, and 4,513,668. These greases, ammunition, and processes have met with varying degrees of success.
Many prior art greases tend to agglomerate or discharge grit and sand which aggravates, rather than inhibits, barrel wear. Such prior art greases often contain silicon or mineral oil which produce a residual cloud of sand or ash at the end of the barrel of the weapon. Such sand and ash may injure the operator's eyes if safety goggles are not worn, interfere with the operator's vision of the target, and pollute the atmosphere.
Some prior art greases suffer from the disadvantages of being too costly or too difficult to apply to either the weapon or the ammunition. Furthermore, many prior art greases are unable to withstand the frictional temperatures and pressures encountered in normal weapon firing over sustained periods of time.
It is, therefore, desirable to provide an improved grease, ammunition, and process which overcomes most, if not all, of the above problems.